Cellulose organic ester composition containing dibutyl malate



Patented Jan. 9, 1934 PATENT OFFICE CELLULOSE ORGANIC ESTER COMPOSI- TION CONTAINING DIBUTYL MALATE Henry B. Smith, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New York No Drawing. Application May 16, 1932 Serial No. 611,759

'7 Claims.

This invention relates to compositions of matter in which cellulose organic esters, such as cellulose acetate, are combined or mixed with other substances, such as a compatible plasticizer, with or without a common solvent for both, and with or without other useful addition agents, so that the resulting product will have properties such as will make the composition highly advantageous for use in the plastic and analogous arts, such, for instance, as the manufacture of wrapping sheets or tissue, photographic film, molding compounds and products-artificial silk, varnishes or lacquers, coating compositions and the like.

One object of this invention is to produce compositions of matter which'may be made into permanently transparent, strong and flexible sheets or films of desired thinness which are substantially waterproof, are unaffected by ordinary photographic fluids and possess the desired properties of a support for sensitive photographic coatings. Another object of my invention is to produce compositions of matter which are capable of easy and convenient manipulation in the plastic and analogous arts, such as in the manufacture of sheets, films, artificial silk filaments, varnishes, lacquers and the like, and to produce compositions which will not injure, or'be injured by, the substances or surfaces with which they are associated during manufacture. Another object of my invention is to produce compositions which can be molded at elevated temperatures and high pressures to produce plastic products having the desirable properties of celluloid. Still another object of my invention is to produce compositions of matter containing cellulose acetate which have a high degree of flexibility, softness and pliability. Other objects will become apparent to those skilled in the art to which this invention pertains.

While cellulose acetate has been known for decades, it has also been known that to utilize it in the various plastic arts it is necessary to mix therewith such plasticizing or conditioning agents as triphenyl phosphate, monochlornaphthalene or the like. Certain of these and other addition agents are also added for the purpose of reducing the inflammability of the product. Plastic inducing agents, such as the higher alcohols and their esters, are sometimes also added. Similarly, addition compounds of various kinds have been employed to increase flexibility, transparency, toughness and other prop erties which will enhance the value of the resulting product. Addition products for the same or similar purposes are also added to cellulose acetate to prepare it for use in the other plastic arts, such as in the manufacture of lacquers, varnishes, artificial silk filaments, molded compounds and the like. While the plasticizers or 50 other addition agents heretofore discovered have had their utility in the art, the increasing use to which cellulose acetate has been put and the increasing number of desirable properties required of cellulose acetate for most purposes have made the discovery of new and economical plasticizers or other addition agents a matter of'considerableimportance to the art. This has been a problem of some difficulty, since many of the nitrocellulose solvents are not solvents-for cellulose acetate, and many substances which act as plasticizers for nitrocellulose are not sufficiently compatible with cellulose acetate to be used as plasticizers in cellulose'acetate compositions.

'Ihave'discovered that valuable properties may be induced in and/or contributed to compositions containing organic esters of cellulose, such as cellulose acetate, by adding thereto as a'plasticizing-compound a di-butyl malate, such as dim-butyl l-malate or di-n-butyl dl-malate. lI-he particularly useful properties which these compounds induce in or contribute to cellulosic compositions containing them are hereinafter enumerated.

In order that those skilled in this art may better understand my invention I would state, by way of illustration, that for the manufacture of photographic film or other sheets my new compositionsof matter may be compounded as follows: parts of acetone-soluble cellulose acetate, i. e. cellulose acetate containing from 36% to 42% acetyl radical, approximately, is dissolved with stirring at atmospheric temperature in SOD-to 500 parts, preferably 400 parts, by 5 weight, of acetone. To this solution may be added from 10 to50 parts, by weight, of di-nbutyl l-malate or oi-di-n-butyl dl-malate. Within the limits stated, the amount of plasticizer may be decreased or increased, depending upon 10 whether it is'desired to decrease or increase, respectively, the properties which these plasticizers contribute to the finished product. The amount of solvent employed may also be increased or decreased, depending upon whether it is desired to have a more or less freely flowing composition, respectively.

Acomposition of matter prepared as above described may be deposited upon any suitable filmforming surface to form a film or sheet, in a manner well known to those skilled in the art. A film so produced has permanently brilliant transparency (even where as much as 50 to parts of the plasticizer per 100 parts of cellulose organic ester, such as cellulose acetate, is used) and low inflammability, burning no more readily than ordinary newsprint. Films containing from 10 parts to 50 parts of di-n-butyl l-malate per 100 parts of cellulose acetate have the unexpected property of superior fiatness-a property which is much sought for in the art but seldom discovered. Films or sheets produced in accordance with my invention are tough and flexible. For instance, films of cellulose acetate plasticized with 20% to 50% (parts by weight based on the cellulose acetate) of di-n-butyl l-malate or of di-n-butyl dl-malate had an initial flexibility of from 35% to 500% greater than that of film containing no plasticizer. Furthermore, film so 'plasticized maintains flexibility in a superior fashion. For instance, films containing 20% to 50% of cli-n-butyl l-malate or of di-n-butyl dlmalate maintained flexibilty at C. for 200 days, whereas an unplasticized film became brittle in 30 days. This indicates that films so plasticized will withstand ordinary usage satisfactorily for many years.

Other similar solvents (instead of acetone) which are compatible with the cellulose acetate .and my new plasticizers will also occur to those skilled in this art, such as ethylene chloridealcohol mixtures. In like manner these plasticizers may be compounded with other single organic esters of cellulose, such as cellulose propionate, butyrate, stearate and the like, or with mixed organic esters, such as cellulose acetostearate, cellulose aceto-propionate, cellulose aceto-butyrate, cellulose aceto-lactate, cellulose aceto-tartrate, or the like, a suitable solvent which will dissolve both the cellulosic derivative and the plasticizer being employed, such, for instance, as an alkylene chloride with or without the addition of alcohol.

Inasmuch as my above-described compositions of matter are useful in the production of films and sheets, it will be apparent that my new plasticizers may also be employed with advantage in the other branches of the plastic art. For instance, my above-described compositions of matter may be employed in the manufacture of artificial silk by the dry spinning method. With the proper coagulating bath they may also be employed for wet spinning. My novel plasticizers may also be employed with advantage in connection with a number of the known lacquer and varnish formulae with which they may be foimd to be compatible. In such cases the plasticizer is usually first put into solution in the cellulose derivative solution, and if non-solvents are added for the purpose of cheapening the composition they are added only to such an extent as will not precipitate the derivative from solu tion. Also the plasticizer is usually employed in rather large amounts, such as from 50 to 60 parts, in compounding lacquers. Other uses within the scope of my invention will also suggest themselves to those skilled in the art and are to be included within the scope of the claims appended hereto.

The di-butyl malates may also be advantageously used as plasticizers in cellulose acetate molding compositions. For instance, when about 30% (parts by weight based on the cellulose acetate) of di-n-butyl l-malate or of di-n-butyl dl-malate is homogeneously mixed with cellulose acetate, the mixture may be converted into a hard, transparent plastic product by molding at a temperature of 140-160" C. and a pressure of from 2500 to 4000 pounds per square inch for a period of from 2 to 5 minutes, in a manner already known to those skilled in molding compounds of that nature.

Moreover, I have found that, upon the addition to cellulose acetate of approximately 100% of di-n-butyl l-malate or of di-n-butyl dl-malate, quite unexpected compatibility of the plasticizer with the cellulose acetate exists and also that quite unexpected flexibility, plasticity and clarity of the final product results. Contrary to experience in most cases where such a large proportion of plasticizer is used, no exudation or crystallizing out of the plasticizer occurs. Compositions containing approximately 100% of a di-butyl malate have great utility where a highly flexible compound is desired, such as in the coating of a base (for instance, cloth or other fabric) in the production of artificial leather, or in the production of relatively thin sheets wherein more than the usual flexibility is important. Such a composition, if converted, for instance, into sheet form will be found to be supple and non-rigid, and to have the ability to conform readily to a surface upon which it may be placed, and this even at atmospheric temperatures.

These novel compositions of matter are produced by merely mixing the plasticizer with cellulose acetate and then adding suflicient of a common solvent, such as acetone, whereupon an intimate mixture of the plasticizer with the cellulose acetate results. The amount of acetone or other common solvent to be employed varies, of course, within rather wide limits depending upon the fluidity of the composition desired. 100 parts of acetone will suffice for many purposes, although we prefer to use its parts. Various high boilers or evaporation retarclents, such as ethyl lactate, amyl acetate or the like may also be added if desired, as is well known in this art.

The compositions of matter so produced may. then be coated into sheets in the usual way by depositing them upon plates or rolls and permitting the solvent to evaporate. If my novel compositions are to be employed in the manufacture of artificial leather, they may be coated upon, for instance, a cloth support and the solvent permitted to evaporate, or the cloth support may be caused to pass through the cellulose acetate-plasticizer composition and permitted to absorb the solution, the solvent in the coating being then permitted to evaporate. In either case, the solvent may, of course, be recovered if desired by condensing the vapors, etc.

While above and in certain of the claims appended hereto, I have ref rred to the use of a, plasticizer in approximately equal proportions, namely in a ratio of approximately 100%, it will be understood that within this terminology variations of from 10% to 15% less than 100% of plasticizer and as much as 25% to 50% more thanv 100% of the plasticizer may in some instances be desirable.

While I have described the use of di-n-butyl l-malate and di-n-butyl dl-malate, it will be obvious that the similar employment of the otherdi-butyl malates is within the scope of my invention.

What I claim as my invention and desire to be secured by Letters Patent of the United States 1s:

1. A composition of matter comprising a cellu lbs 5. A composition of matter comprising 100 parts of cellulose acetate and about 10 to 100 parts, by weight, of di-butyl malate as a plasticizer for the cellulose acetate.

6. A relatively thin, flexible sheet comprising 100 parts of cellulose acetate and about 10 to 100 parts, by Weight, of di-butyl malate.

'7. A molding composition adapted for molding under elevated temperatures and high pressures, comprising cellulose acetate and. di-butyl malate as a plasticizer for the cellulose acetate.

HENRY B. SMITH. 

